GCN Circular 14566

GRB 130505A: MAXI/GSC detection

S. Nakahira (JAXA), M. Serino (RIKEN), H. Negoro (Nihon U.),
S. Ueno, H. Tomida, M. Kimura, M. Ishikawa (JAXA),
T. Mihara, M. Sugizaki, M. Morii, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Nakano (AGU),
H. Tsunemi, M. Sasaki (Osaka U.),
M. Nakajima, T. Onodera, K. Fukushima, K. Suzuki (Nihon U.),
Y. Ueda, M. Shidatsu, T. Kawamuro, (Kyoto U.),
Y. Tsuboi, M. Higa (Chuo U.),
M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.),
K. Yamaoka (Nagoya U.) report on behalf of the MAXI team

At 2013-05-05T08:22:29 UT, the MAXI/GSC detected an uncatalogued X-ray
transient source. Assuming that the source flux was constant over the
transit, we obtain the source position at
(R.A., Dec.) = (136.955 deg, 17.585 deg)= (09 07 49 , +17 35 05)(J2000)
with a 90% C.L. statistical error of 0.07 deg and an additional systematic
uncertainty of 0.1 deg (90% containment radius).

The position and time are consistent with those of GRB 130505A (Cannizzo
et al, GCN #14563). The transit by MAXI occurred from
2013-05-05T08:22:18 (=T0-10 s, where T0 is the Swift/BAT trigger time) to T0+40s.
The averaged X-ray flux was 3.17 +/- 0.21 Crab (2-20 keV).
The spectrum is fitted by a power-law model with a photon index of
1.37 (-0.10/+0.10). There was no significant excess flux at the previous
transit at 2013/05/05 06:46 UT and at the next transit at 2013/05/05
09:55 UT with an upper limit of 20 mCrab for each.